Building Flutter Engine from source

See also:

• Compiling the engine
• Custom Flutter Engine Embedders
• Custom Flutter Engine Embedding in AOT Mode

0. Use pre-build image

You can also download a specific libflutter_engine.so version from https://github.com/sony/flutter-embedded-linux/releases/latest without building yourself. Currently, we are watiching the official stable channel version.

However, please note that Flutter Engine is using many third-party software libraries. So you need to build the Flutter Engine yourself by following the steps below if you want to check all software licenses.

1. Install build tools

$ git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git
$ export PATH=$PATH:$(pwd)/depot_tools

Python 2

Python 2 is required to build. If you default installation is Python 3 you could workaround this by using virtualenv:

$ virtualenv .env -p python2
$ source .env/bin/activate

See also: https://github.com/dart-lang/sdk/wiki/Building#python-2

2. Create .gclient file

When using the latest version of Flutter Engine

It isn't recommended using the latest version unless you want to build the Engine. At the moment, we recommend the beta channel version.

solutions = [
  {
    "managed": False,
    "name": "src/flutter",
    "url": "https://github.com/flutter/engine.git",
    "custom_deps": {},
    "deps_file": "DEPS",
    "safesync_url": "",
    "custom_vars" : {
      "download_android_deps" : False,
      "download_windows_deps" : False,
    },
  },
]

When using a specific version of Flutter Engine

You can check the current engine version (commit-id / SHA):

• master channel
• dev channel
• beta channel
• stable channel

See also: https://github.com/flutter/flutter/wiki/Flutter-build-release-channels

You can also get the engine version from ${path_to_flutter_sdk_install}/flutter/bin/internal/engine.version of the Flutter SDK which you are currently using.

solutions = [
  {
    "managed": False,
    "name": "src/flutter",
    "url": "https://github.com/flutter/engine.git@FLUTTER_ENGINE",
    "custom_deps": {},
    "deps_file": "DEPS",
    "safesync_url": "",
    "custom_vars" : {
      "download_android_deps" : False,
      "download_windows_deps" : False,
    },
  },
]

Note: Replace FLUTTER_ENGINE with the commid it of the Flutter engine you want to use.

3. Get source files

$ gclient sync

4. Build embedder

$ cd src

arm64 targets with debug mode

$ ./flutter/tools/gn --target-os linux --linux-cpu arm64 --runtime-mode debug --unoptimized --embedder-for-target --disable-desktop-embeddings
$ ninja -C out/linux_debug_unopt_arm64

arm64 targets with profile mode

$ ./flutter/tools/gn --target-os linux --linux-cpu arm64 --runtime-mode profile --no-lto --embedder-for-target --disable-desktop-embeddings
$ ninja -C out/linux_profile_arm64

arm64 targets with release mode

$ ./flutter/tools/gn --target-os linux --linux-cpu arm64 --runtime-mode release --embedder-for-target --disable-desktop-embeddings
$ ninja -C out/linux_release_arm64

x64 targets with debug mode

$ ./flutter/tools/gn --runtime-mode debug --unoptimized --embedder-for-target --disable-desktop-embeddings
$ ninja -C out/host_debug_unopt

x64 targets with profile mode

$ ./flutter/tools/gn --runtime-mode profile --no-lto --embedder-for-target --disable-desktop-embeddings
$ ninja -C out/host_profile

x64 targets with release mode

$ ./flutter/tools/gn --runtime-mode release --embedder-for-target --disable-desktop-embeddings
$ ninja -C out/host_release

5. Install embedder library

$ cp ./out/${path to your selected target and mode}/libflutter_engine.so <path_to_cmake_build_directory>

Supplement

You need to install libflutter_engine.so in <path_to_cmake_build_directory> to build. But you can switch quickly between debug / profile / release modes for the Flutter app without replacing libflutter_engine.so by using LD_LIBRARY_PATH when you run the Flutter app.

$ LD_LIBRARY_PATH=<path_to_engine> ./flutter-client <path_to_flutter_project_bundle>

# e.g. Run in debug mode
$ LD_LIBRARY_PATH=/usr/lib/flutter_engine/debug/ ./flutter-client ./sample/build/linux/x64/debug/bundle

# e.g. Run in profile mode
$ LD_LIBRARY_PATH=/usr/lib/flutter_engine/profile/ ./flutter-client ./sample/build/linux/x64/profile/bundle

# e.g. Run in release mode
$ LD_LIBRARY_PATH=/usr/lib/flutter_engine/release/ ./flutter-client ./sample/build/linux/x64/release/bundle

clang_x64/gen_snapshot

If you want to cross-build for arm64 on x64, you need to use out/linux_*_arm64/clang_x64/gen_snapshot later. See also: https://github.com/sony/flutter-embedded-linux/wiki/Building-Flutter-apps#cross-build-for-arm64-targets-on-x64-hosts